Terrestrial television and radio broadcast networks have made use of high power transmitters covering broad service areas, which enable one-way distribution of content to user equipment such as televisions and radios. By contrast, wireless telecommunications networks have made use of low power transmitters, which have covered relatively small areas known as “cells”. Unlike broadcast networks, wireless networks may be adapted to provide two-way interactive services between users of user equipment such as telephones and computer equipment.
The introduction of cellular communications systems in the late 1970's and early 1980's represented a significant advance in mobile communications. The networks of this period may be commonly known as first generation, or “1G” systems. These systems were based upon analog, circuit-switching technology, the most prominent of these systems may have been the advanced mobile phone system (AMPS). Second generation, or “2G” systems ushered improvements in performance over 1G systems and introduced digital technology to mobile communications. Exemplary 2G systems include the global system for mobile communications (GSM), digital AMPS (D-AMPS), and code division multiple access (CDMA). Many of these systems have been designed according to the paradigm of the traditional telephony architecture, often focused on circuit-switched services, voice traffic, and supported data transfer rates up to 14.4 kbits/s. Higher data rates were achieved through the deployment of “2.5G” networks, many of which were adapted to existing 2G network infrastructures. The 2.5G networks began the introduction of packet-switching technology in wireless networks. However, it is the evolution of third generation, or “3G” technology that may introduce fully packet-switched networks, which support high-speed data communications.
The multiple broadcast/multicast service (MBMS) is an IP datacast service, which may be deployed in EDGE and UMTS networks. The impact of MBMS is largely within the network in which a network element adapted to MBMS, the broadcast multicast service center (BM-SC), interacts with other network elements within a GSM or UMTS system to manage the distribution of content among cells within a network. User equipment may be required to support functions for the activation and deactivation of MBMS bearer service. MBMS may be adapted for delivery of video and audio information over wireless networks to user equipment. MBMS may be integrated with other services offered over the wireless network to realize multimedia services, such as multicasting, which may require two-way interaction with user equipment.
Standards for digital television terrestrial broadcasting (DTTB) have evolved around the world with different systems being adopted in different regions. The three leading DTTB systems are, the advanced standards technical committee (ATSC) system, the digital video broadcast terrestrial (DVB-T) system, and the integrated service digital broadcasting terrestrial (ISDB-T) system. The ATSC system has largely been adopted in North America, South America, Taiwan, and South Korea. This system adapts trellis coding and 8-level vestigial sideband (8-VSB) modulation. The DVB-T system has largely been adopted in Europe, the Middle East, Australia, as well as parts of Africa and parts of Asia. The DVB-T system adapts coded orthogonal frequency division multiplexing (COFDM). The ISDB-T system has been adopted in Japan and adapts bandwidth segmented transmission orthogonal frequency division multiplexing (BST-OFDM). The various DTTB systems may differ in important aspects; some systems employ a 6 MHz channel separation, while others may employ 7 MHz or 8 MHz channel separations.
Planning for the allocation of frequency spectrum may also vary among countries with some countries integrating frequency allocation for DTTB services into the existing allocation plan for legacy analog broadcasting systems. In such instances, broadcast towers for DTTB may be co-located with broadcast towers for analog broadcasting services with both services being allocated similar geographic broadcast coverage areas. In other countries, frequency allocation planning may involve the deployment of single frequency networks (SFNs), in which a plurality of towers, possibly with overlapping geographic broadcast coverage areas (also known as “gap fillers”), may simultaneously broadcast identical digital signals. SFNs may provide very efficient use of broadcast spectrum as a single frequency may be used to broadcast over a large coverage area in contrast to some of the conventional systems, which may be used for analog broadcasting, in which gap fillers transmit at different frequencies to avoid interference.
Even among countries adopting a common DTTB system, variations may exist in parameters adapted in a specific national implementation. For example, DVB-T not only supports a plurality of modulation schemes, comprising quadrature phase shift keying (QPSK), 16-QAM, and 64 level QAM (64-QAM), but DVB-T offers a plurality of choices for the number of modulation carriers to be used in the COFDM scheme. The “2K” mode permits 1,705 carrier frequencies that may carry symbols, each with a useful duration of 224 μs for an 8 MHz channel. In the “8K” mode there are 6,817 carrier frequencies, each with a useful symbol duration of 896 μs for an 8 MHz channel. In SFN implementations, the 2K mode may provide comparatively higher data rates but smaller geographical coverage areas than may be the case with the 8K mode. Different countries adopting the same system may also employ different channel separation schemes.
While 3G systems are evolving to provide integrated voice, multimedia, and data services to mobile user equipment, there may be compelling reasons for adapting DTTB systems for this purpose. One of the more notable reasons may be the high data rates that may be supported in DTTB systems. For example, DVB-T may support data rates of 15 Mbits/s in an 8 MHz channel in a wide area SFN. There are also significant challenges in deploying broadcast services to mobile user equipment. Many handheld portable devices, for example, may require that services consume minimum power to extend battery life to a level which may be acceptable to users. Another consideration is the Doppler effect in moving user equipment, which may cause inter-symbol interference in received signals. Among the three major DTTB systems, ISDB-T was originally designed to support broadcast services to mobile user equipment. While DVB-T may not have been originally designed to support mobility broadcast services, a number of adaptations have been made to provide support for mobile broadcast capability. The adaptation of DVB-T to mobile broadcasting is commonly known as DVB handheld (DVB-H).
To meet requirements for mobile broadcasting the DVB-H specification may support time slicing to reduce power consumption at the user equipment, addition of a 4K mode to enable network operators to make tradeoffs between the advantages of the 2K mode and those of the 8K mode, and an additional level of forward error correction on multiprotocol encapsulated data—forward error correction (MPE-FEC) to make DVB-H transmissions more robust to the challenges presented by mobile reception of signals and to potential limitations in antenna designs for handheld user equipment. DVB-H may also use the DVB-T modulation schemes, like QPSK and 16-quadrature amplitude modulation (16-QAM), which may be most resilient to transmission errors. MPEG audio and video services may be more resilient to error than data, thus additional forward error correction may not be required to meet DTTB service objectives.
Time slicing may reduce power consumption in user equipment by increasing the burstiness of data transmission. Instead of transmitting data at the received rate, under time slicing techniques, the transmitter may delay the sending of data to user equipment and send data later but at a higher bit rate. This may reduce total data transmission time over the air, which may be used to temporarily power down the receiver at the user equipment. Time slicing may also facilitate service handovers as user equipment moves from one cell to another because the delay time imposed by time slicing may be used to monitor transmitters in neighboring cells. The MPE-FEC may comprise Reed-Solomon coding of IP data packets, or packets using other data protocols. The 4K mode in DVB-H may utilize 3,409 carriers, each with a useful duration of 448 μs for an 8 MHz channel. The 4K mode may enable network operators to realize greater flexibility in network design at minimum additional cost. Importantly, DVB-T and DVB-H may coexist in the same geographical area. Transmission parameter signaling (TPS) bits that are carried in the header of transmitted messages may indicate whether a given DVB transmission is DVB-T or DVB-H, in addition to indicating whether DVB-H specific features, such as time slicing, or MPE-FEC are to be performed at the receiver. As time slicing may be a mandatory feature of DVB-H, an indication of time slicing in the TPS may indicate that the received information is from a DVB-H service.
Present developments in the communication technology may adapt broadcasting to mobility services. However, broadcasting may often require high bit rate data transmission at rates higher than could be supported by existing mobile communications networks. Furthermore, downlink communication paths which may be utilized for communicating information to one or more receivers may deteriorate. In this regard, significant delays may be experienced at the receiver side for receiving the communicated information. In addition, quality of the received information communicated via a deteriorated downlink communication path may also decrease.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one skilled in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.